The present invention relates to a flow cytometer, imaging flow cytometer or similar particle analyzer for analyzing a liquid specimen containing particles such as blood and urine, or more particularly to a particle analyzer excellent in analyzing capability and which possesses a detection unit (image sensor) capable of obtaining the morphological information of particles flowing in the flow cell in real time and a signal processing unit, and moreover to an apparatus for analyzing particles by emitting light to the particles in a liquid specimen (blood, urine, or the like) moving as a sheath flow, focusing the transmission light image on a one-dimensional image sensor (line sensor), and processing the obtained detection signal, and more specifically to a particle analyzer capable of obtaining absorption (extinction) information, morphological information and the like of individual particles in real time.
Hitherto, as the particle analyzer using a flow cell, an apparatus as shown in FIG. 1 is known. In this apparatus, laser beams from a laser source 100 are directed to particles flowing in a sheath flow in a flow cell 106, which are optically scanned in a direction which crosses with a particle flow direction (the surface-reverse direction in the sheet) by a polarizer (including a lens) 102. Optical signals obtained from the parts of the particles to be analyzed are detected by optical detectors 114, 116, so that more specific morphological information may be obtained for individual particles. Numeral 104 denotes a controller, 108, 110 are objective lenses, 112 is a dichroic mirror, 118, 120 are A/D converters, and 122 is a signal processor. The sheath flow, meanwhile, refers to a flow surrounded by a suspension of particles covered with a laminar sheath liquid in order to align particles neatly in one row and precisely in the middle of the flow to allow passage.
In order to scan using laser beams, this apparatus requires an expensive light polarizing element (polarizer 102) and its control device (controller 104) utilizing the acousto-optical effect or electro-optical effect. Besides, the laser beams must usually be reduced to a very thin level of 2 .mu.m or less, and it is necessary to scan the laser beam stable and accurately with respect to the flowing position of the particles.
In other prior art, a so-called slit scan apparatus is known, in which laser beams are reduced to about 1 .mu.m and emitted in the flow direction of the particles, and the detection signal waveform of the scattered light or the fluorescence obtained at this time is analyzed to obtain more specific information about the particles. In this apparatus, specific information which divides each particle two-dimensionally is not obtained. That is, it does not possess resolution in the direction vertical to the particle flow direction, and as compared with the apparatus shown in FIG. 1 or the apparatus of the present invention described below, the quantity of information obtained about the particle to be analyzed is smaller, and the precision is lower.
On the other hand, the Japanese Laid-open Patent Hei. 1-270644 discloses a particle analyzer with scanning light beams in a direction crossing the particle passing direction, detecting the light transmitted inside the particle by a photo detector, and obtaining the image information of the particle.
The Japanese Laid-open Patent Hei. 2-105041 discloses a particle measuring apparatus for receiving transmitted light by an array type photo detector disposed at the conjugate position with the detecting part, by improving the apparatus disclosed in the above Japanese Laid-open Patent Hei. 1-270644.
The Japanese Laid-open Patent Sho. 52-113272 discloses an apparatus for scanning a spot light by a flying spot tube in the midst of passing of a biological cell specimen through a flow cell, and obtaining the color information and morphological information (area and shape) of the cell.
The Japanese Laid-open Patent Sho. 62-254037 discloses a construction in which a flow cytometer is furnished with a streak imaging device, where detection of particles by the imaging device are performed almost simultaneously, and an imaging signal is processed only when matched with a predetermined characteristic value, that is, only the particle of specific characteristic is imaged. As the imaging device, sampling imaging by using a one-dimensional image sensor is also unveiled.
The Japanese Laid-open Patent Hei. 3-123840 discloses a construction in which a moving object such as iron ore is taken by a one-dimensional image sensor, and the particle size distribution of the object is determined on the basis of a two-dimensional image data obtained by accumulating a one-dimensional image data.
U.S. Pat. No. 4,338,024 (Application No. 146064) and Japanese Patent Publication Sho. 57-500995 (the original application being the above U.S. patent application Ser. No. 146064) relate to a construction in which a flat sample liquid flow is formed, that is, a flat sheath flow is formed, and particle images are taken.
In the apparatus disclosed in the Japanese Laid-open Patents Hei. 1-270644, Hei. 2-105041 and Sho. 52-113272, light beams are scanned, and special devices are needed, yet stable scanning is difficult.
The apparatus disclosed in Japanese Laid-open Patent Hei. 3-123840 relates to an apparatus for measuring the particle size of material such as iron ore charged in a blast furnace. The field of this apparatus thus differs from that of the present invention. Incidentally, nothing is mentioned about real time processing of the accumulated image data or determination of parameters such as absorption quantity, area and peripheral length.
In the Japanese Laid-open Patents Sho. 62-254037 and Hei. 3-123840, nothing is mentioned about the flat flow of a sample liquid flow. By flat flow, the quantity of analysis may be increased.
U.S. Pat. No. 4,338,024 and Japanese Patent Publication Sho. 57-500995 refer to forming of flat sample liquid flow as stated above, but the provision of a "one-dimensional image sensor for producing an image signal upon every scanning by forming a flat sample liquid flow, and processing means for processing signal and operating on the basis of the image signal from the sensor" is not mentioned in any one of these seven patent publications.
Besides, as the apparatus for extracting and analyzing the features of particles moving in a fluid, the flow cytometer and cell sorter have been hitherto known widely.
In the conventional flow cytometer, the morphological information of particles (area, circumferential length, etc.) could not be obtained. By passing the specimen in a flat sheath flow, emitting a strobe light, and processing the image taken by a video camera, the absorption quantity and morphological information of particles may be obtained in real time, but it requires a video camera and an exclusive image processing device, which means a higher cost. Yet, since the strobe light is emitted to image at a specific interval of one frame period (1/30 second) of the video camera, particles of low concentration cannot be captured on all image frames at high efficiency. Hence, there are problems in the sample processing ability and repeatability or accuracy of results of the analysis.
U.S. Pat. No. 4,338,024 and Japanese Patent Publication Sho. 57-500995 refer to forming of flat sample liquid flow as stated above, but none of these seven publications mentions anything about "the one-dimensional image sensor for producing an image signal upon every scanning by forming a flat sample liquid flow, and determination of absorption quantity and morphological information of the particle by processing the signal on the basis of the image signal from this sensor, and determination of the information in real time every time the particle passes through the detection unit".